PL185283B1 - Method of and apparatus for obtaining filler containing polyurethane products - Google Patents

Abstract

1 . A method for producing polyurethanes containing fillers, in which the polyol component is pre-mixed with the filler in a mechanical mixer, and then the mixture is fed to the mixer, characterized in that a screw mixer (55) containing a screw is used as a mechanical mixer. full-plate type, in which the gap between the screw and the screw housing is set to 2 to 4 times the width of the average filler grain, then the mixture is fed to the mixer (1) using a screw pump or, respectively, a single-impeller screw pump, wherein the pressure inside the pump does not exceed 20 1 0 5 Pa, and the pressure of the mixture at the entrance to the mixer does not exceed 2 1 0 5 Pa, then isocyanate is injected into the polyol component containing the filler under a pressure of 50 · 1 0 5 P to 250 · 105 Pa, and the mixture of polyisocyanate with polyaddition agents is introduced into a continuous or discontinuous form and hardens. 5. Device for producing polyurethanes containing fillers, equipped with a dosing device for the filler, a dosing device for the polyol, a mixer and a pump supplying the mixture to the mixer, characterized in that the mixer is for mixing the filler and polyol, bananas and a screw mixer (55), in which the gap between the screw and the screw housing is 1.5 to 2.5 mm, and furthermore includes a non-pressurized intermediate tank (56) for the polyol component containing the filler, a screw pump or a single-impeller screw pump transporting the mixture to the mixer (1) and the mixer for mixing the polyol component containing the filler with the isocyanate component, while feeding (11) the polyol component containing the filler to the mixing chamber (13) the mixing chamber itself and the connected conduit (2) until to discharge the mixture have substantially equal diameters, and the mixing chamber is only an indefinite area in terms of its size in the direction of flow, in which one or more inlet holes (12, 12a, 12b) for the isocyanate component terminate. F and g . 1a PL PL PL

Description

The present invention relates to a method and an apparatus for the production of filler-containing polyurethanes.

The production of polyurethanes containing fillers is carried out in such a way that the components of the polyisocyanate mixture with polyaddition agents and the fillers are introduced into a mixer with an agitator, mixed there, and then introduced into an open or closed mold or a continuously movable mold formed by the system.

185 283 of a double conveyor belt, the reaction mixture, if necessary, hardening after closing the mold, and then the molded part is removed from the mold. The filler can hereby be pre-mixed with the polyol component. There have also been proposals to pre-blend the liquid components of the polyisocyanate reaction mixture with polyaddition agents in a countercurrent injection mixer and then blend the fillers with the reaction mixture in a friction mixer.

Depending on the properties of the solids used, a number of problems can arise when using this method. Coarse fillers with a particle size of, for example, greater than 0.5 mm, or mechanically sensitive fillers, for example encapsulated fillers, can, due to the high shear forces, be mechanically damaged in the above-described mixing aggregates, such as agitator mixers or friction mixers. Fillers, which are prone to sedimentation, can become deposited in the supply lines when mixed with one of the reaction components, even in the event of short production breaks. Furthermore, they tend to deposit in the reactive mixture of polyisocyanate with polyaddition agents and accumulate in the lower part of the mold.

For example, there are many proposals for the addition of expandable graphite in order to impart fire-retardant properties to polyurethanes, in particular polyurethane foam, e.g. from US-A 3 574 644, DE-A-24 28 307, EP-A 192 888 and EP-A 337 228.

Examples of suitable porous graphite are the known interstitial compounds SO _X , NO _X , halogen and / or strong graphite acids. They are also referred to as graphite salts. Porous graphites which emit SO ₂ , SO ₃ , NO and / or NO ₂ when forming bubbles at temperatures of, for example, 120-350 ° C, are preferred. The porous graphite may be in the form of platelets with a maximum diameter in the range 0.1-5 mm. Preferably, the diameter is 0.5-3 mm. Such porous graphites are commercially available.

With regard to the ready-to-use flame-retardant insulating element, it is possible to use, for example, from 1 to 50% by weight. porous graphite. Preferably, the content of the porous graphite is 2-30% by weight, more preferably 2-20% by weight. The performance of porous graphite as a fire retardant is dependent on the size of the graphite platelets. During the binder process, the ground porous graphite particles contribute very little to the fire retardant equipment. Conventional methods of introducing fillers into polyurethane reaction mixtures result in a significant reduction in particle size which is disadvantageous to fire retardant equipment. Particularly in the production of polyurethane foam containing porous graphite, strong sedimentation of the porous graphite is still observed due to the not yet cured foam. As a result, the rigid polyurethane insulation boards, which have fire-resistant properties due to the porous graphite, have an increased content of porous graphite on the lower side (relative to the position in the double belt conveyor system), while the upper side is poor in porous graphite.

None of the aforementioned publications dealing with equipping polyurethane foam with fire retardant components provide guidance on introducing porous graphite into the foam. Therefore, porous graphite has not yet been used as a fire retardant in polyurethane insulations.

The present invention proposes, on the one hand, a method and a suitable device for gently introducing porous graphite into the polyurethane reaction mixture, and, on the other hand, proposing a method and suitable means for reducing or preventing sedimentation of the porous graphite in the liquid foam.

However, the invention is not limited to incorporating graphite into polyurethane but is generally used to incorporate mechanically sensitive fillers into polyurethanes. Such fillers are, for example, short glass fibers, which generally break during insertion and as a result lose some of their reinforcement properties.

A further example is the incorporation of iron oxide pigments in the manufacture of insulating materials in an electromagnetic radiation shield.

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DE-A1-2945818 discloses a process for the production of polyurethanes in which a filler component is injected into a mixer under low pressure, and both the isocyanate and the polyol formulation are introduced under high pressure.

EP-A-554719 discloses a mixer which is used for the production of prepolymers. As the components mixed in the mixer have a comparatively low viscosity, the components according to EP-A-554719 can be dosed into the mixer with a low pre-pressure, for example 3 10 ⁵ Pa.

EP-A-431388 relates to the avoidance of undesirable introductions of air when the fillers are mixed with the polyol component and the subsequent mixing of the filler-containing polyol component with the isocyanate in mixers. Mechanically sensitive fillers cannot, however, be mixed in this way as they would be crushed in the mixers.

A method for the production of filler-containing polyurethanes, in which the polyol component is premixed with the filler in a mechanical mixer, and then the mixture is fed to the mixer, according to the invention, characterized in that the mechanical mixer is a screw mixer containing a full-plate screw, in which the gap between the screw is and the screw housing is set to 2 to 4 times the width of the average grain size of the filler, then the mixture is fed to the mixer by means of a screw pump or a single-thread screw pump, the pressure inside the pump not exceeding 20 10 ⁵ Pa, and the pressure of the mixture at the input to the mixer is set at not exceeding 2 · 10 5 Pa *, and a polyol component containing a filler is injected into the isocyanate at a pressure of from 50 · 10 ³ Pa to 250 · 10 ³ Pa, and a mixture of polyisocyanate with means introduced Polyaddition to the continuous form or the form n intermittent and hardens.

In the process of the invention, porous graphite is used as filler.

Preferably, the filler-containing polyol is collected indirectly in a non-pressurized intermediate tank for a residence period of no more than 20 seconds.

1 to 30 vol.% Is incorporated into the filler-containing polyol component. air and / or nitrogen.

A device for the production of polyurethanes containing fillers, equipped with a dosing device for the filler, a dosing device for the polyol, a mixer and a pump for supplying the mixture to the mixer, according to the invention, is characterized in that the mixer for mixing the filler and polyol is a screw mixer in which the gap between the screw and the screw housing is 1.5 to 2.5 mm, and further includes a non-pressurized intermediate tank for the filler-containing polyol component, a screw pump or single-impeller screw pump for transferring the mixture into the mixer, and a mixer for mixing the filler-containing polyol component with the isocyanate component, wherein supplying the filler-containing polyol component to the mixing chamber, the mixing chamber itself and the associated conduit until the mixture is discharged have a substantially equal diameter, and the mixing chamber only constitutes an undefined area in terms of its size in the direction of the mixture. A flow path ending with one or more isocyanate component inlet openings and the mixing vessel cross-sectional area is 10 to 100 times greater than the sum of the isocyanate component inlet cross-sectional areas.

Preferably, in the apparatus of the invention, the cross-sectional area of the mixer is 30 to 100 times greater than the sum of the cross-sectional areas of the inlet openings for the isocyanate component.

Moreover, the mixing chamber according to the invention has no movable or stationary swirl baffles.

Preferably, two to four inlet openings are provided for the isocyanate component. The inlet openings for the isocyanate component may be located in a plane transverse to the flow direction in the mixing chamber. Where provided for

The plurality of inlet openings for the isocyanate component are then preferably disposed in a plurality of consecutive planes.

The pressure of the filler-containing polyol component at the inlet to the mixing chamber is preferably 0.2 to 2 · 10 ⁵ Pa, more preferably 1 · 1.5 · 10 ⁵ Pa. The isocyanate component may be injected into the mixing chamber at a pressure of 50 · 250 · 10 ⁵ Pa, but preferably above 100 · 10 ⁵ Pa.

The velocity of the incoming polyol component should be at least 1 m / s, preferably 2-5 m / s. The flow velocity of the isocyanate component is preferably 80-150 m / s.

With the method of the present invention, it is possible to use mechanically sensitive fillers, in particular expandable graphite, in polyurethanes. The fillers are not exposed to a pressure higher than 20 · 10 ⁵ Pa during the introduction. Pressures of up to 10 10 ⁵ Pa are preferably exerted.

The subject of the invention is illustrated in the embodiment in the drawing, in which Figs. A and 1b show the mixer of the device according to the invention with an outlet shaped as a wide-slot nozzle, Fig. 2 shows the mixer of the device according to the invention with an outlet formed as a bearing or tongue nozzle, Fig. 3a and 3b show the mixer of the device according to the invention for injection operation, Figures 4a, 4b and 4c show an alternative embodiment of the mixer of the device according to the invention for injection operation, Figure 5 schematically shows the device according to the invention for producing polyurethane insulation boards containing fillers.

The mixer 1 of the apparatus according to the invention (Fig. 1a) comprises a feed line 11 for the filler-containing polyol as well as isocyanate inlet openings. The inlet openings in the form of injection nozzles 12 have movable closing cones 15 directed towards the pre-tensioned springs, which open when the isocyanate (arrow 14) is supplied at the required pressure. The mixing zone 13, which is not precisely defined in terms of geometry, is designed as a straight flow tube into which the injection nozzles 12 for the isocyanate discharge. The mixing zone 13 does not contain any partitions creating vortices. Preferably, the isocyanate injection nozzles 12 are not directed to the axis of mixing zone 13, but are twisted in a plane perpendicular to the axis so that the filler-containing polyol stream is swirled in mixing zone 13 by the injection of the isocyanate. The outlet 2 of the mixer 1 is in the form of a wide slot nozzle. Fig. 1b shows the outlet 2 of the mixer in a cross section perpendicular to the plane of Fig. 1a.

FIG. 2 shows a mixer 1 as in FIG. 1a, the outlet 2 being in the form of a tab nozzle.

The mixer 1 according to Fig. 3a is designed for a discontinuous injection operation to produce foam parts of a mold. The mixer includes a closing piston 20 that is hydraulically moveable in the axial direction (arrow 21). In order to fill the mold, the closing piston 20 (as indicated by arrow 21) is retracted, allowing the inlet 11 for the filler-containing polyol and the injection nozzle 12 for the isocyanate to enter the mixing zone 13. From the mixing zone 13, the mixture arrives an outlet pipe 2 through which the mixture flows into the mold. After filling the mold, the closing piston 20 moves to the position shown, the inlets 11 and 12 to the mixing zone 13 are closed. At the same time, the inlets 11 and 12 are connected via grooves 28 and 29 of the closing piston 20 with recirculation lines 24 and 25 through which the filler-containing polyol and isocyanate are returned to the appropriate hopper. During the interruption of the shot, the recycle flow is maintained, as is the case in the polyurethane manufacturing technique. Furthermore, the agitator includes a hydraulically actuated cleaning piston 26 which, upon completion of the shot, ejects the mixture remaining in the outlet pipe 2 after the closing piston 20 has been moved to the closing position 2. In Fig. 3b, the agitator of Fig. 3a is shown in section A-A. In an exemplary embodiment, three injection nozzles are provided for introducing the isocyanate.

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According to the invention, it is important in comparison to the isocyanate inlet openings that the polyol feed line has a large cross-section with correspondingly large cross-sections for the recirculation lines, so that the filler-containing polyol can be transported essentially without pressure.

FIG. 4a shows an alternative embodiment of the mixer of the inventive apparatus for discontinuous injection operation, while keeping slight angular variations for the filler-containing polyol. The same reference numerals refer to the same elements in Fig. 3a. Fig. 4b shows the section from Fig. 4a in section B-B. Fig. 4c shows the mixer of Fig. 4a with the closing piston 20 having been moved to the closed position. The filler-containing polyol stream fed through line 11 only changes direction by an angle of 20 to 35 when entering mixing zone 13. The introduction of the isocyanate (four paired opposing inlets 12a and 12b) is transverse to the polyol stream. The isocyanate feed lines 14a and 14b are shown in pairs so that the polyol stream is displaced in the feed planes by swirling in a counter-rotating manner. After injection is completed, recirculation of the isocyanate passes through the grooves 29 of the closure plunger 20. Recirculation of the filler-containing polyol is conducted through bore 28 through closure plunger 20 which communicates with the recirculation line 24 in the closed position.

Figure 5 shows schematically the device according to the invention for the gentle (gentle) introduction of fillers into polyurethanes. The filler, in particular expandable graphite, is transported from the hopper 51 by a dosing screw 52 to the screw mixer 55. The polyol is transported from the hopper 53 via the metering pump 54 also to the screw mixer 55. From the screw mixer 55, the polyol containing the filler reaches the hopper 56 by controlling the level 61, the volume of the filler-containing polyol stock is dimensioned such that the residence time does not exceed 8-20 sec. Due to the short residence time in the storage hopper 56, sedimentation of the filler in the reservoir hopper is avoided. By means of a low-speed screw pump 57, the filler-containing polyol is transported to the gassing device 58, which is configured as a flow tank. The gassing takes place by means of a hollow conical stirrer 60, into which air or nitrogen 59 is fed through the hollow shaft. From the gassing tank 58, the gas-charged polyol component containing the filler enters the mixer 1. In the mixing zone 13, isocyanate is injected under pressure from the hopper 62 via a dosing pump 63. At the outlet 2 of mixer 1, a wide swing of a polyisocyanate mixture containing a filler with polyaddition agents is produced, which is applied to the conveyor belt 70 traveling in the direction of arrow 71 of the block foaming system. In order to separate the mixture transversely across the width of the conveyor belt, the mixer 1 is moved by a reciprocating movement, indicated by the arrow 72. The gas dissolved in the mixture is released as fine bubbles on the filler particles as it exits the mixer 1, so that the filler particles do not deposit in the resulting liquid foam 73. In the event of discontinuous operation of the mixer (mixer as shown in FIGS. 3 and 4), to form part of the mold, isocyanate is recirculated at the time the injection is interrupted into the hopper 62 and the polyol containing the filler is returned to the hopper 56.

The production of the filler-containing polyol component is preferably carried out as follows:

The filler is dosed via dosing screws 52 by belt dosing scales or articulated shaking conveyors and fed to the screw mixer 55 for mixing with the polyol.

The pitch, wall torsion, length and rotational speed are preferably so matched to each other that friction and pressure build-up in the screw are minimized. In a preferred embodiment, the screw mixer has a continuous screw conveyor (plate screw) which leaves a free gap to the screw housing which is larger than the grain size of the filler.

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Preferably, the gap width is 2 to 4 times the average grain size. When using porous graphite with an average grain size of 0.6-0.8 mm (plate diameter), the gap between the screw and the housing is preferably 1.5-2.5 mm. The H / D screw pitch (winding pitch divided by diameter) can be 0.8 to 1.5. The rotational speed of the screw is preferably selected such that the shear in the slot to the screw housing does not exceed 30 / s, in particular the rotational speed is 10 to 25 / s.

From the screw mixer 55, the polyol component is fed to a storage hopper, which serves as a reservoir on the suction side for a metering pump 57 for transporting the filler-containing polyol component to the mixer 1. Screw pumps or single-impeller screw pumps are suitable as metering pumps and are operated in the range low pressure up to 20 10 ⁵ Pa of the internal pressure of the pump, i.e. in the rotational speed range 300-500 rpm.

Preferably, between the metering pump 57 and the mixer is a gassing device 58 to which air and / or nitrogen are introduced in amounts of 1-30 vol.% (Normal conditions), based on polyol, to the filler-containing polyol component. Taking into account the amount of air already dissolved in the polyol under the influence of storage, the amount of air in the polyol after gasification should be 10-30% by volume. Preferably, the gassing is performed in a flow-through tank by means of a hollow agitator 60, preferably by means of a conical hollow agitator. Under the prevailing pressure, the gas dissolves completely. After expansion of the polyisocyanate reaction mixture with polyaddition agents downstream of the mixer to normal pressure, the mixture is supersaturated with gas, whereby air bubbles are separated on the filler molecules as bubble spores, which counteract sedimentation of the filler in the liquid polyurethane foam.

In the case of continuous production of polyurethane foam, the filler-containing polyisocyanate reaction mixture with polyaddition agents is preferably applied via conical hollow nozzles, tongue nozzles, spoon nozzles or wide-slotted nozzles to the lower belt conveyor 70 of the double belt system. Tongue nozzles which are commercially available under the name Z1 to Z4 from Lechler, Metzingen, Germany are particularly preferred. With such nozzles, a wide flat jet with precisely limited injection can be produced. Preferably, the flat stream is directed parallel to the direction of travel of the conveyor belt, the mixer with the discharge device reciprocating across the entire width of the conveyor belt.

Example

Component A is a mixture consisting of 85 parts of a polyol formulation with a viscosity of about 2000 mPa · s (25 ° C) and a hydroxyl number of 590 mg KOH / g, commercially available as Bayer VP.PU 22HB96 from Bayer AG, Leverkusen, 15 parts of tris (chloroisopropyl) phosphate (TCPP), 2 parts of stabilizer, commercially available as Tegostab B8421 from Goldschmidt AG, Essen, 1.6 parts of activator, commercially available as Demorapid 726b from Bayer AG, Leverkusen, and 2.0 parts water. Component A was mixed in a screw mixer with 25 parts by weight of porous graphite available under the trade name Sigraflex® FR from SGL Carbon. A mixture of 160 parts by weight of polyisocyanate, available under the name Desmodur 44V70L from Bayer AG, and 8 parts by weight of n-pentane (quantitative data per unit time) were injected into the mixer. The double belt conveyor system produces an insulation board with a thickness of 10 cm and a raw density of 34 kg / m ³ . The porous graphite is distributed evenly across the plate thickness. Flammability test according to DIN 4102, part 1. The insulation board meets the requirements of building material class B2.

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Publishing Department of the UP RP. Circulation of 60 copies

Price 4.00 PLN.

Claims (6)

Patent claims A method for the production of polyurethanes containing fillers, in which the polyol component is pre-mixed with the filler in a mechanical mixer, and then the mixture is fed to the mixer, characterized in that a screw mixer (55) containing a full-plate screw is used as the mechanical mixer. between the screw and the screw housing is set to 2 to 4 times the width of the average grain size of the filler, then the mixture is fed to the mixer (1) by means of a screw pump (57) or a single-rotor screw pump, the pressure inside the pump not exceeding 20 10 ⁵ a, and the pressure of the mixture at the inlet to the mixer does not exceed 2 10 ⁵ Pa, then the isocyanate is injected into the polyol component containing the filler under a pressure of 50 105 Pa to 250-105 Pa, and the mixture of polyisocyanate with polyaddition agents is introduced into a continuous form relatively discontinuous and hardens. 2. The method according to p. The process of claim 1, wherein the filler is porous graphite. 3. The method according to p. The method of claim 1 or 2, characterized in that the filler-containing polyol is collected indirectly in a non-pressurized intermediate tank for a residence time of no more than 20 seconds. 4. The method according to p. The method of claim 1 or 2, characterized in that 1 to 30 vol.% Is added to the filler-containing polyol component. air and / or nitrogen. 5. A device for producing polyurethanes containing fillers, equipped with a filler dosing device, a polyol dosing device, a mixer and a pump for delivering the mixture to the mixer, characterized in that the mixer for mixing the filler and polyol is a screw mixer (55), in which the gap between the screw and the screw housing is 1.5 to 2.5 mm and further comprises a non-pressurized intermediate tank (56) for the filler-containing polyol component, a screw pump (57) or a single-rotor screw pump conveying the mixture to the mixer (1) and a mixer for mixing the filler-containing polyol component with the isocyanate component, the supply (11) of the filler-containing polyol component to the mixing chamber (13) the mixing chamber itself and the attached line (2) until the mixture is discharged are of substantially equal diameter, and the mixing chamber is only an undefined area in terms of its size in the direction of flow ending with one or more inlet openings (12, 12a, 12b) for the isocyanate component and the cross sectional area of the mixer is 10 to 100 times greater than the sum of the cross sectional areas of the isocyanate component inlet openings. 6. The device according to claim 1 5. The method of claim 5, characterized in that the cross-sectional area of the mixer (1) is 30 to 100 times greater than the sum of the cross-sectional areas of the inlet openings (12, 12a, 12b) for the isocyanate component.